Question: why does a liquid turn into a gas?

Paul Brack answered on 18 Jun 2015:

Everything is made up out of molecules (or atoms). Heat is a measure of how much energy the molecules have. In a solid, the molecules have some energy, and they are always vibrating, but they same roughly in the same place, so the object remains solid. When molecules get a bit more energy (or get heated up a bit more), they start to move around. In a liquid, the molecules are sliding around over each other, so they are still interacting, just not as much as in a solid, and so liquids can flow. However, if you heat up the liquid, and give the molecules even more energy, eventually they just rampage off into space. The molecules are now so far apart they are barely interacting with other molecules, and this is a called a gas.